This invention relates to a microwave enhanced method and an apparatus therefor.
Recently, electron cyclotron resonance chemical vapor deposition (ECR CVD) has attracted the interests of researchers as a new method of manufacturing thin films, particularly amorphous thin films. For example, Matsuo et al discloses one type of such a ECR CVD apparatus in U.S. Pat. No. 4,401,054. This recent technique utilizes microwaves to energize a reactive gas into a plasma state by virtue of a magnetic field which functions to pinch the plasma gas within the excitation space. With this configuration, the reactive gas can absorb the energy of the microwaves. A substrate to be coated is located distant from the excitation space (resonating space) for preventing the same from being sputtered.) The energized gas is showered on the substrate from the resonating space. In order to establish an electron cyclotron resonance, the pressure in a resonating space is kept at 1xc3x9710xe2x88x923 to 1xc3x9710xe2x88x925 Torr at which electrons can be considered as independent particles, and resonate with a microwave in an electron cyclotron resonance on a certain surface on which the magnetic field takes a particular strength required for ECR. The excited plasma is extracted from the resonating space, by means of a divergent magnetic field, to a deposition space which is located distant from the resonating space and in which is disposed a substrate to be coated.
In such a prior art method, it is very difficult to form a thin film of a polycrystalline or single-crystalline structure, so that currently available methods are almost limited to processes for manufacturing amourphous films. Also, high energy chemical vapor reaction is difficult to take place in accordance with such a prior art method and therefore a diamond film or other films having high melting points, or uniform films on an even surface having depressions and caves can not be formed.
It is therefore an object of the invention to provide a microwave enhanced CVD method and an apparatus therefor capable of forming a film, which can not be formed by the prior art method, such as a diamond film, or a film of a material having a high melting point.
According to one aspect of the invention, the surface of an object to be coated is located in a region of a resonating space in which the electric field of a microwave takes its maximum value. By this configuration, the deposition can be carried out while the deposited film is being partially sputtered, and therefore, e.g., a diamond film can be formed.
According to another aspect of the invention, a new CVD process has been achieved. The new Process utilizes a mixed cyclotron resonance which was derived first by the inventors. In the new type of exciting process, interaction of reactive gas itself must be taken into consideration as a non-negligible perturbation besides the magnetic field and microwave, and therefore charged particles of a reactive gas can be absorbed in a relatively very wide resonating space. For the mixed resonance, the pressure in a reaction chamber is elevated 102xe2x88x92105 times as high as that of the prior art method.